# Pressure drop along a water pipe

by bellshom
Tags: pipe, pressure, water
 P: 21 Along a horizontal pipe I am getting a pressure drop of roughly 10-20 kPa every 20 metres in a 6.5" (OD) water pipe. This seems much to high and I am thinking the pipe may be stuffed and thus there is to much friction which is reducing the pressure of the water. Just wanted to get some other thoughts on the matter. The pipe is horizontal and the pipe is straight with no water being taken from the pipe along the measured points.
 P: 459 What is the flow through the pipe?
 P: 21 Do u mean flow rate, if so then it is unknown.
P: 459

## Pressure drop along a water pipe

You really need to know the flow rate to determine whether the pressure drop is high or not.
 P: 737 K. A few comments: 1. 10-20 kPa is translates to around 1.5-3 psi. This is a large difference when talking about pressure drops due to friction at the same location...Is it safe to assume, then, that this system has changing flow rates? 2. Is this fluid a slurry or a mixture of some kind? You could of course have issues with settling if it is. 3. For high capacity systems, losing 10 kPa every 20 meters isn't a rarity. For instance, a 6 inch pipe will lose 10 kPa every 20 meters at around 55 L/s (~870 USgal/min). The flow required to lose that pressure in a 6.5" pipe will be somewhat higher, and even more so for the 20 kPa (i'd estimate around 1500 USgal/min), but these are by no means extraordinary flow rates. You really need to know the conditions of your system to know whether or not things are acting properly.
 P: 21 The fluid is processed water. The conditions of the system are to difficult to determine, different things use water a different times. So the flow through the pipe would be hard to determine without installing a gauge somewhere to measure the flow.
 P: 737 Without knowing the flow, I'm afraid there's not much that can be said about the problem. Something could be "stuffing" the pipe, though with process water it seems somewhat doubtful, especially if your pump impellers survive for a reasonable amount of time. More likely you have high flow and a rough inner pipe surface which combine to get your headloss. If you must find out the answer, you should look into finding a company which has access to an Ultrasonic Flow Meter. This you will strap to the outside of the pipe, assuming it is bare pipe, and following the strict directions and geometries, you can get a pretty good estimate of the flow.

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